309. Elastica.—India-rubber.
Caoutchouc. (U.S.P. VIII)
The prepared milk-juice of He'vea Braziliensis Mueller and other species, known in commerce as Para rubber. Large trees containing a milky juice which, on hardening, forms india-rubber. Ficus elastica, producing the greatest quantity, has its seeds germinate in the forks of the tree, giving off aerial roots which descend to the ground and form a great many trunks.
HABITAT.—South America and India, the finest quality coming from Brazil.
DESCRIPTION.—Large, flat pieces, or molded into various shapes-balls, hollow, bottle-shaped pieces, etc. When the juice first hardens it is yellowish-brown externally and yellowish-white within, but in the processes of molding and drying it acquires a smoky, blackish appearance; very elastic; odor peculiar. Insoluble in water and alcohol, but soluble in chloroform, carbon bisulphide, and benzin. The common adulterants are the carbonates of zinc and lead; when pure or nearly pure, india-rubber should float in water.
CONSTITUENTS.—The elastic principle has been termed caoutchoucin; it, or a similar principle, is contained in a great number of milky-juiced plants.
USES.—On account of its insolubility it has no therapeutic application, but is extensively used in the arts. Employed in some of the pharmaceutical plasters, e.g., Emp. Elasticum. U.S. IX.
